Small, gasoline-fueled internal combustion engines, such as those found on golf carts, lawn mowers, snow blowers, chain saws and other, similar outdoor equipment are usually simple and inexpensive. Many of these engines, for example, include a common gasoline carburetor controlled by a throttle cable that directly controls both air and fuel intake through the carburetor. In order to remain inexpensive, however, these simple gasoline-fueled internal combustion engines do not include emission controlling features and are, therefore, a great source of atmospheric pollutants.
In response to the surprisingly large amount of pollutants produced by these small engines, the Environmental Protection Agency has recently issued new regulations requiring small engines to comply with the 1990 Clean Air Act. Small engine manufacturers, accordingly, are scrambling for simple and inexpensive modifications that will allow their engines to meet these new, more stringent emission requirements.
One solution for providing small engines that meet the new emission requirements is to convert them from gasoline burning engines to cleaner gaseous fuel, such a natural gas or butane, burning engines. Preferably, a gaseous fuel injection system is provided as a direct replacement for the gasoline carburetor.
Gaseous fuel injection systems, of course, are known as illustrated by the following patents. However, none of the following patents, alone or in combination, disclose a gaseous fuel injection system providing a direct replacement for a gasoline carburetor controlled by a throttle cable that directly controls both air and fuel intake.
U.S. Pat. No. 4,433,664 to Rodrigues, for example, discloses a fuel system utilizing gaseous fuel. The system includes a fuel supply tank connected to a feeder gasket by a discharge line controlled by a pressure regulator. The pressure regulator regulates the flow of fuel to the feeder gasket, which is secured between a carburetor and an intake manifold. A vacuum control, connected to the intake manifold by a tube, controls the pressure regulator and is in-turn controlled by the strength of a vacuum created within the intake manifold. The air intake of the carburetor is controlled by an accelerator pedal, and an operator can alter the vacuum in the intake manifold, and therefore indirectly control the fuel consumption, by pressing on the pedal to increase the air intake into the carburetor.
U.S. Pat. No. 3,651,794 to Douglas discloses an accelerator control system for gaseous fuel. The system includes a fuel supply tank connected to a fuel intake manifold by a fuel line controlled by a pressure regulator. The pressure regulator is directly connected to an accelerator pedal and controls fuel flow into the fuel intake manifold. The fuel intake manifold includes flow circuits leading to injection passageways connected to each cylinder of the engine, with each flow circuit having a manually adjusted restriction valve for effecting equal flow to all cylinders.
U.S. Pat. No. 5,377,646 to Chasteen discloses a gaseous fuel delivery system. The system includes a fuel delivery bar positioned across an air intake tube leading to a manifold of an engine. The fuel delivery bar has a plurality of fuel delivery orifices for dispersing fuel into the air intake tube, and is positioned above a butterfly valve controlling air intake. Fuel is metered to the fuel delivery bar by a valve cone controlled by a sensor monitoring oxygen in the exhaust gases. The butterfly valve is operated by a throttle to directly control the amount of oxygen entering the air intake tube and exiting in the exhaust, so that the throttle indirectly controls fuel flow.
U.S. Pat. No. 3,710,770 to Newkirk et al. discloses a fuel system for gaseous fuel. A circular manifold is positioned in a carburetor of an engine for dispersing fuel through a plurality of check valves in the manifold. A pressure regulator is controlled by an operator to act as a throttle to control fuel flow, and is also connected to a butterfly valve in the manifold to control air intake. It is not disclosed how the pressure regulator is controlled by the operator, or connected to the air intake valve.
Accordingly, what is desired is a gaseous fuel injection system that will provide a direct replacement for a gasoline carburetor, accommodate a throttle cable normally connected to the gasoline carburetor and allow the throttle cable to directly control both air and fuel intake into the engine. Such a gaseous fuel injection system will allow an internal combustion engine to be easily converted to operate on a gaseous fuel such as natural gas or butane, for example.